Noninvasive techniques for studying the function of the outer retinal an choroid will be furthur developed. Human cone photopigment kinetics will be investigated with color matching in normal observers and patients with retinal and choroidal diseases. Color matches depend on the effective concentration of the photopigments. The concentration of the photopigments is controlled by both the rate at which the photopigments are being bleached (due to the absorption of light), and the rate at which they are being regenerated (due to biochemical ractions taking place in both the photoreceptors and the retinal pigment epithelium). Measuring changes in color matches as a function of both time and retinal illuminance will quantify these processes. The mechanisms underlying the abnormally high illuminance required to bleach the photopigments in some diabetics will be investigated. These techniques will also be used to study the natural history of retinal and choroidal diseases such as retinitis pigmentosa and central serous ritnopathy. The use of tests that localize functional abnormalities may provide information crucial to understanding the etiology of retinal and choroidal diseases, and may aid in determining a patient's prognosis. Comparison of the bleaching and regeneration of the photopigments of normal observers to the bleaching and regeneration of the photopigments in patients will provide a better understanding of the nature of the photopigment kinetics. Inter- and intra-observer differences in the photopigments of the retina will also be studied.